1. Field of the Invention
The present invention relates to a continuous decatizing machine.
2. Description of the Prior Art
German Offenlegunschrift No. 2,148,311 relates to a continuous decatizing machine, with a rotatable and heatable decatizing cylinder, the wall of which has a plurality of holes. A backing cloth is applied against the material to be processed, along a portion of the circumference of the cylinder. This backing cloth consists of a material which is impermeable to air, and the holes in the cylinder wall communicate with a low-pressure source to produce a suction action from outside inwards.
Due to the different flow conditions prevailing in the area between the holes of the cylinder and the cylinder surfaces lying therebetween, the processed material is not likely to be of uniform quality; indeed, the material, as regards appearance, brightness, and feel, will exhibit differences and will be unattractive.
In addition, the use of a backing cloth which is impermeable to air, adversely affects the surface of the material to be treated. In this respect, since the inner side of the backing cloth facing the material to be decatized must be in the form of a textile material, the outer side of the backing cloth consists of rubber or other impermeable material, the backing cloth thus being of multi-layer constructions. However, practice has shown that with such a backing cloth, surface pressures in excess of 0.5 kp/cm.sup.2 causes lines and patterns to be formed on the inner surface structure of the backing cloth, and render the decatized material, at least in the case of materials dyed in the piece, unusable.
In addition the inner side of the backing cloth is exposed to very considerable wear with the result that the working life of the backing cloth is relatively short, and the backing cloth is relatively expensive to replace owing to its multi-layer construction.
In this previously proposed machine, moistening of the material by water or the like occurs before processing on the heated cylinder. Firstly, the absorption of moisture by the material during relatively fast operation is not at an optimum value. The moisture supplied is provided only on the surface and on one side of the material, and as the time of operation is short, it does not penetrate to the inside of the assembly of fibres. Thus, with the surface pressure treatment, an adequate fixing effect cannot be obtained. Therefore material thus produced is not shrink-resistant.
Further, the decatizing effect is provided only on a single side. The evaporation of the water introduced takes place spontaneously under the vacuum conditions so that with continued processing increasing amounts of moisture are removed from the material, and the material is subject to considerable drying-out as a result of the surface pressure and the heat effects. As a consequence of this phenomenon, a single-side decatizing effect is produced with an undesirable high gloss. The drying-out of the material causes the material to have a brittle feel, as a result of which the thickness of the material is reduced considerably.
The moistening of the material with water or the like before the decatizing treatment is non-uniform due to soiling and blockages in the moistening units, brought about by chalk deposits or the like as a result of continued operation of the machine. Non-uniform moistening, in turn, leads to non-uniform decatizing effects.
An object of the invention is to improve this previously proposed machine in such a manner that throughout the entire material, and on both sides of it, a uniform and permanent gloss, a pleasant feel and, in addition, complete shrink stability are obtained.